Laying pipe or conduit in excavated trenches is an inherently dangerous task. Even in relatively stable ground, there is always a risk that the trench walls may collapse and injure or kill workmen in the trench. Further, even if such collapses do not cause injury, time and effort are lost when the trench has to be redug. These risks of collapse increase with the depth of the trench, which may range from five or six feet to 25-30 feet or more. The risks are even greater if the ground contains is especially rocky and/or wet and/or contains other like obstacles.
Various safety devices have been developed address these issues. Perhaps the most common such device is the trench box. A trench box is simply a large hollow floorless rectangular box with a pair of parallel elongated sidewalls connected by either by narrow front and back walls or support members called “spreaders”. The trench box is sized to fit into the trench being dug to shore up the walls and prevent its collapse while workmen lay pipe therein. The trench box is typically made of a structural material, such as steel, of sufficient thickness to hold its shape even when the trench walls begin to collapse in on it. Typically, an excavating machine, such as a trackhoe, is used to excavate a trench in advance of the trench box. The trench is made slightly wider than the trench box. Once the pipe is laid at the bottom of the trench within the trench box, the trench box may be pulled forward into a newly dug trench portion for continuing the pipe-laying procedure. When a deep trench is required, the trench boxes are merely stacked one on top of the other until the desired height is reached.
One alternative to using a trench box is to slope the walls of the trench back at an angle of repose such that the walls are not likely to collapse into the trench. This means that the excavator must remove considerably more earth from the trench, adding time and expense to the job. Another alternative is to simply dig the trench and work within as is—an option that is still popular with some excavators.
In addition to the safety issues, there are other problems complicating the task of laying pipe in excavated trenches. For example, each section of pipe must be properly aligned to fit into the pre-existing laid pipe. Further, it is often necessary to deal with obstacles such as damaged pipe sections or fittings, rocks, and the like; dealing with such obstacles takes time and often requires specialized tools. Often, these tools are bulky and the use of such specialized tools requires removal of the trench box and a widening of the trench to accommodate the tools. This adds time and risk to the job.
Also, there is typically no mechanism for depositing gravel or stone filler material over the laid pipe. Further, it remains difficult to maintain the grade and alignment of the conduit being laid in the trench. In the past, this was done almost always done manually via best-guess work and estimation; currently, lasers are used to assist in alignment. Moreover, it is time consuming, if not especially difficult, for the operator to lower the pipe into the trench and/or position the pipe. Thus, there remains a need for an improved bracing box for laying pipe in a trench. The present invention addresses this need.